The present invention concerns a method for calculating the boundary layer level between fluids, in particular the boundary layer level between oil and water in connection with the use of a segment-based boundary layer meter.
In many different contexts, such as a separator in a process system or production installation for oil and gas, in which water is an undesired component, it may be desirable to determine the level of the respective fluids (oil, water and gas) in the separator. The purpose of such a measurement may, for example, be to control the level in the separator. To achieve good level control, the level measurement must be “robust” and consistent. For level measurement of the water level in separators, however, this may be a challenge on account of an emulsion of oil and water.
In connection with the measurement of the level of fluids, it is possible to use a so-called profile meter that is designed to detect the boundary between the various phases (each fluid or the mixture of fluids). The profile meter consists of a large number of segments arranged in a vertical row above/below each other. Each segment is designed to detect a state or property in connection with the fluid to be detected, and emits a signal to a registration/calculation unit. Such meters may, for example, be based on inductive measurement, capacitive measurement or radioactive sources.
For most prior art profile meters, it is difficult to detect changes in density for the respective fluid(s) or fluid mixture(s), which means that the measurements may contain a lot of “noise”. Furthermore, the measurements are not very continuous, as a standard algorithm used for the prior art solutions selects the “correct” segment for the phase change, based on the use of the registrations from 2 segments, for the level calculation by means of linear interpolation.